Potential antigenic targets used in immunological tests for diagnosis of tegumentary leishmaniasis: A systematic review.

Immunological tests may represent valuable tools for the diagnosis of human tegumentary leishmaniasis (TL) due to their simple execution, less invasive nature and potential use as a point-of-care test. Indeed, several antigenic targets have been used with the aim of improving the restricted scenario for TL-diagnosis. We performed a worldwide systematic review to identify antigenic targets that have been evaluated for the main clinical forms of TL, such as cutaneous (CL) and mucosal (ML) leishmaniasis. Included were original studies evaluating the sensitivity and specificity of immunological tests for human-TL, CL and/or ML diagnosis using purified or recombinant proteins, synthetic peptides or polyclonal or monoclonal antibodies to detect Leishmania-specific antibodies or antigens. The review methodology followed PRISMA guidelines and all selected studies were evaluated in accordance with QUADAS-2. Thirty-eight original studies from four databases fulfilled the selection criteria. A total of 79 antigens were evaluated for the detection of antibodies as a diagnostic for TL, CL and/or ML by ELISA. Furthermore, three antibodies were evaluated for the detection of antigen by immunochromatographic test (ICT) and immunohistochemistry (IHC) for CL-diagnosis. Several antigenic targets showed 100% of sensitivity and specificity, suggesting potential use for TL-diagnosis in its different clinical manifestations. However, a high number of proof-of-concept studies reinforce the need for further analysis aimed at verifying true diagnostic accuracy in clinical practice.

GK1 Improves the Immune Response Induced by Dendritic Cells of BALB/c Mice Infected with Leishmania mexicana Promastigotes.

PURPOSE: Dendritic cells (DCs) are the most potent antigen-presenting cells (APCs), and their capacity to activate the immune response has been widely used in immunotherapies against different diseases, predominantly cancer. However, they have not been so widely used in immunotherapies against infectious diseases. Leishmania mexicana is the causative agent of cutaneous leishmaniasis in Mexico, which can result in localized cutaneous leishmaniasis (LCL) and diffuse cutaneous leishmaniasis (DCL). DCL is characterized by the incapability of the immune response to control the parasite, which thus disseminates to all teguments. Treatments against DCL have shown low efficacy, which is a reason why alternative therapies such as immunotherapies are promising. One adjuvant that has proven its effectiveness in immunotherapies against some cancers and infections is GK1, a component of the SPVac vaccine against porcine cysticercosis. GK1 has the capacity to elicit proinflammatory cytokines and chemokines from DCs and macrophages. METHODS: We pulsed bone marrow-derived dendritic cells (BMDCs) with GK1 and a lysate obtained from L. mexicana promastigotes and tested the efficacy of this combination against the infection of susceptible mice with L. mexicana. RESULTS: We found that BMDCs stimulated with GK1 and a lysate of L. mexicana promastigotes secreted IFN-γ and IL-12, and when they were adoptively transferred to BALB/c mice which were then infected with L. mexicana promastigotes, there was a reduction in the size of the lesion and in the parasite load. CONCLUSIONS: The adjuvant properties of GK1 along with parasite antigens may have a protective effect against the infection of BALB/c mice with L. mexicana.

Host and parasite responses in human diffuse cutaneous leishmaniasis caused by L. amazonensis.

Diffuse cutaneous leishmaniasis (DCL) is a rare form of leishmaniasis where parasites grow uncontrolled in diffuse lesions across the skin. Meta-transcriptomic analysis of biopsies from DCL patients infected with Leishmania amazonensis demonstrated an infiltration of atypical B cells producing a surprising preponderance of the IgG4 isotype. DCL lesions contained minimal CD8+ T cell transcripts and no evidence of persistent TH2 responses. Whereas localized disease exhibited activated (so-called M1) macrophage presence, transcripts in DCL suggested a regulatory macrophage (R-Mϕ) phenotype with higher levels of ABCB5, DCSTAMP, SPP1, SLAMF9, PPARG, MMPs, and TM4SF19. The high levels of parasite transcripts in DCL and the remarkable uniformity among patients afforded a unique opportunity to study parasite gene expression in this disease. Patterns of parasite gene expression in DCL more closely resembled in vitro parasite growth in resting macrophages, in the absence of T cells. In contrast, parasite gene expression in LCL revealed 336 parasite genes that were differently upregulated, relative to DCL and in vitro macrophage growth, and these transcripts may represent transcripts that are produced by the parasite in response to host immune pressure.

Promastigote parasites cultured from the lesions of patients with mucosal leishmaniasis are more resistant to oxidative stress than promastigotes from a cutaneous lesion.

Human leishmaniasis caused by Leishmania (Viannia) braziliensis can be presented as localized cutaneous leishmaniasis (LCL) or mucosal leishmaniasis (ML). Macrophages kill parasites using nitric oxide (NO) and reactive oxygen species (ROS). The aim of this study was to evaluate the ability of parasites obtained from patients with LCL or ML to produce and resist NO or ROS. Promastigotes and amastigotes from LCL or ML isolates produced similar amounts of NO in culture. Promastigotes from ML isolates were more resistant to NO and H2O2 than LCL parasites in a stationary phase, whereas amastigotes from LCL isolates were more resistant to NO. In addition, in the stationary phase, promastigote isolates from patients with ML expressed more thiol-specific antioxidant protein (TSA) than LCL isolates. Therefore it is suggested that infective promastigotes from ML isolates are more resistant to microbicidal mechanisms in the initial phase of infection. Subsequently, amastigotes lose this resistance. This behavior of ML parasites can decrease the number of parasites capable of stimulating the host immune response shortly after the infection establishment.

PD-L1 May Mediate T-Cell Exhaustion in a Case of Early Diffuse Leishmaniasis Caused by Leishmania (L.) amazonensis.

Introduction: Diffuse cutaneous leishmaniasis (DCL) is a rare disease form associated with Leishmania (L.) amazonensis in South America. It represents the "anergic" pole of American Tegumentary Leishmaniasis, and the explanation for its resistance to treatment remains elusive. We aimed to study some possible immunological mechanisms involved in the poor DCL treatment response by evaluating some cell surface molecules obtained from a patient with DCL by flow cytometry. Case presentation: A 65-year-old DCL patient who initially failed to respond to the standard treatment for the disease showed vacuolated macrophages filled with amastigotes in lesion biopsy, and L. (L.) amazonensis was identified through ITS1PCR amplification. The Leishmania skin test and indirect immunofluorescence analysis revealed negative results. Peripheral blood from the patient was collected after a few months of treatment, when the patient presented with no lesion. Peripheral blood mononuclear cells were analyzed ex vivo and in vitro after 48 h of stimulation with soluble L. (L.) amazonensis antigen (SLA). Cell death, surface molecules, and intracellular molecules, such as IFN-γ and granzyme B, were analyzed in the cells using flow cytometry. Analysis of the surface markers showed an increased expression of the inhibitory molecule programmed death ligand 1 (PD-L1) in the monocytes restimulated with SLA (approximately 65%), whereas the negative controls were 35% positive for PD-L1. Conversely, compared with the negative controls, we observed a decrease in CD4+IFN-γ+ T cells (8.32 versus 1.7%) and CD8+IFN-γ+ T cells (14% versus 1%). We also observed a relevant decrease in the granzyme B levels in the CD8+ T cells, from 31% in the negative controls to 5% after SLA restimulation. Conclusion: The dysfunctional activation of PD-L1 inhibitory pathway after Leishmania antigen stimulation and reduced levels of IFN-gamma and granzyme B-producing cells could be closely related to unresponssiveness to standard drug treatment of DCL patient.

The role of the P2X7 receptor in murine cutaneous leishmaniasis: aspects of inflammation and parasite control.

Leishmania amazonensis is the etiological agent of diffuse cutaneous leishmaniasis. The immunopathology of leishmaniasis caused by L. amazonensis infection is dependent on the pathogenic role of effector CD4+ T cells. Purinergic signalling has been implicated in resistance to infection by different intracellular parasites. In this study, we evaluated the role of the P2X7 receptor in modulating the immune response and susceptibility to infection by L. amazonensis. We found that P2X7-deficient mice are more susceptible to L. amazonensis infection than wild-type (WT) mice. P2X7 deletion resulted in increased lesion size and parasite load. Our histological analysis showed an increase in cell infiltration in infected footpads of P2X7-deficient mice. Analysis of the cytokine profile in footpad homogenates showed increased levels of IFN-γ and decreased TGF-ß production in P2X7-deficient mice, suggesting an exaggerated pro-inflammatory response. In addition, we observed that CD4+ and CD8+ T cells from infected P2X7-deficient mice exhibit a higher proliferative capacity than infected WT mice. These data suggest that P2X7 receptor plays a key role in parasite control by regulating T effector cells and inflammation during L. amazonensis infection.

Importância da resolvinas na infecção por Leishmania Amazonensis / Importance of resolvins in Leishmania Amazonensis infection

A Leishmaniose Cutânea Difusa (LCD) é uma manifestação clínica. rara causada pela Leishmania amazonensis que é caracterizada por uma resposta celular. parasitária ineficiente e macrófagos intensamente parasitados nas lesões cutâneas.. Mediadores lipídicos e seus precursores desempenham um papel crucial durante a. infecção por Leishmania. Estudos prévios demonstram que pacientes com leishmaniose. tegumentar, exibem um distinto balanço de eicosanoides in situ e sistêmico.. Recentemente, demonstrou-se que mediadores lipídicos especializados na pró-resolução. desempenham um papel crítico na redução de processos inflamatórios patológicos. induzindo a restauração da homeostasia em diferentes modelos experimentais. Entre. esses mediadores, as resolvinas da série D exibem potente atividade anti-inflamatória e. imuno-regulatória que inclui a inibição da quimiotaxia leucocitária e bloqueio na. produção de citocinas pró-inflamatórias. No entanto, ainda é desconhecido se as. resolvinas desempenham um papel significativo no estabelecimento e persistência da. infecção por Leishmania. OBJETIVO: Nesse estudo, avaliamos os níveis circulantes. de Resolvina D1 (RvD1) em pacientes com leishmaniose tegumentar apresentando a. forma clínica cutânea localizada (LCL) ou difusa. RESULTADOS: Nossos resultados. demonstram que pacientes com LCD apresentam maiores níveis plasmáticos de RvD1. quando comparados a LCL ou controles endêmicos. Além disso, os níveis séricos de. RvD1 em pacientes com LCD se correlacionam positivamente com a Arginase I e TGF-. β, enquanto que inversamente com os níveis sistêmicos de TNF-α. Experimentos. adicionais in vitro utilizando macrófagos humanos revelaram que a RvD1 promove a. replicação intracelular da L. amazonensis por um mecanismo associado a indução da. enzima heme oxigenase-1. CONCLUSÃO: Os resultados sugerem que a via de. produção da RvD1 pode servir como uma potencial estratégia terapêutica para os. pacientes com LCD.

INTRODUCTION: Diffuse Cutaneous Leishmaniasis (DCL) is a rare clinical manifestation caused by Leishmania amazonensis that is characterized by an inefficient parasite-specific cellular responses and heavily parasitized macrophages in skin lesions. Lipid mediators and their precursors play a crucial role during Leishmania infection. Previous works have shown that patients with cutaneous leishmaniasis exhibit a distinct in situ and systemic balance of this eicosanoids. Recently, pro-resolution lipid mediators have been shown to play critical role in dampening pathological inflammatory processes to reestablish homeostasis in a diverse range of experimental settings. Among these mediators, resolvins from D series have been described to exhibit potent antiinflammatory and immune-regulatory activities that include inhibition of leukocyte chemotaxis and blockage on the production of proinflammatory cytokines. However, whether resolvins play significant roles in establishment and persistence of Leishmania infection is currently unknown. AIM: We addressed this question by assessing circulating levels of resolvin D1 (RvD1) in tegumentary leishmaniasis patients presenting localized cutaneous leishmaniasis (LCL) or diffuse disease. RESULTS: We found that DCL patients have higher plasma levels of RvD1 when compared with LCL patients or endemic controls. In addition, the levels of this mediator were positively correlated with arginase-I and TGF-β and were negatively correlated with TNF-α levels. Additional in vitro experiments using primary human macrophages revealed that resolvin D1 promotes the intracellular L. amazonensis replication for a mechanism dependent on induction of heme oxygenase-1 enzyme. CONCLUSION: These results indicate that targeting RvD1 could serve as potential strategy for DCL patients.

Regulation of Leishmania (L.) amazonensis protein expression by host T cell dependent responses: differential expression of oligopeptidase B, tryparedoxin peroxidase and HSP70 isoforms in amastigotes isolated from BALB/c and BALB/c nude mice.

Leishmaniasis is an important disease that affects 12 million people in 88 countries, with 2 million new cases every year. Leishmania amazonensis is an important agent in Brazil, leading to clinical forms varying from localized (LCL) to diffuse cutaneous leishmaniasis (DCL). One interesting issue rarely analyzed is how host immune response affects Leishmania phenotype and virulence. Aiming to study the effect of host immune system on Leishmania proteins we compared proteomes of amastigotes isolated from BALB/c and BALB/c nude mice. The athymic nude mice may resemble patients with diffuse cutaneous leishmaniasis, considered T-cell hyposensitive or anergic to Leishmania's antigens. This work is the first to compare modifications in amastigotes' proteomes driven by host immune response. Among the 44 differentially expressed spots, there were proteins related to oxidative/nitrosative stress and proteases. Some correspond to known Leishmania virulence factors such as OPB and tryparedoxin peroxidase. Specific isoforms of these two proteins were increased in parasites from nude mice, suggesting that T cells probably restrain their posttranslational modifications in BALB/c mice. On the other hand, an isoform of HSP70 was increased in amastigotes from BALB/c mice. We believe our study may allow identification of potential virulence factors and ways of regulating their expression.

PKDL and other dermal lesions in HIV co-infected patients with Leishmaniasis: review of clinical presentation in relation to immune responses.

BACKGROUND: Co-infection of leishmaniasis and HIV is increasingly reported. The clinical presentation of leishmaniasis is determined by the host immune response to the parasite; as a consequence, this presentation will be influenced by HIV-induced immunosuppression. As leishmaniasis commonly affects the skin, increasing immunosuppression changes the clinical presentation, such as in post-kala-azar dermal leishmaniasis (PKDL) and cutaneous leishmaniasis (CL); dermal lesions are also commonly reported in visceral leishmaniasis (VL) and HIV co-infection. METHODS: We reviewed the literature with regard to dermal manifestations in leishmaniasis and HIV co-infection, in three clinical syndromes, according to the primary presentation: PKDL, VL, or CL. RESULTS: A wide variety of descriptions of dermal leishmaniasis in HIV co-infection has been reported. Lesions are commonly described as florid, symmetrical, non-ulcerating, nodular lesions with atypical distribution and numerous parasites. Pre-existing, unrelated dermal lesions may become parasitized. Parasites lose their tropism and no longer exclusively cause VL or CL. PKDL in HIV co-infected patients is more common and more severe and is not restricted to Leishmania donovani. In VL, dermal lesions occur in up to 18% of patients and may present as (severe) localized cutaneous leishmaniasis, disseminated cutaneous leishmaniasis (DL) or diffuse cutaneous leishmaniasis (DCL); there may be an overlap with para-kala-azar dermal leishmaniasis. In CL, dissemination in the skin may occur resembling DL or DCL; subsequent spread to the viscera may follow. Mucosal lesions are commonly found in VL or CL and HIV co-infection. Classical mucocutaneous leishmaniasis is more severe. Immune reconstitution disease (IRD) is uncommon in HIV co-infected patients with leishmaniasis on antiretroviral treatment (ART). CONCLUSION: With increasing immunosuppression, the clinical syndromes of CL, VL, and PKDL become more severe and may overlap. These syndromes may be best described as VL with disseminated cutaneous lesions (before, during, or after VL) and disseminated cutaneous leishmaniasis with or without visceralization.

Comparative analysis of the tissue inflammatory response in human cutaneous and disseminated leishmaniasis

Cutaneous leishmaniasis (CL) is the most frequent clinical form of tegumentary leishmaniasis and is characterised by a single or a few ulcerated skin lesions that may disseminate into multiple ulcers and papules, which characterise disseminated leishmaniasis (DL). In this study, cells were quantified using immunohistochemistry and haematoxylin and eosin staining (CD4+, CD68+, CD20+, plasma cells and neutrophils) and histopathology was used to determine the level of inflammation in biopsies from patients with early CL, late CL and DL (ulcers and papules). The histopathology showed differences in the epidermis between the papules and ulcers from DL. An analysis of the cells present in the tissues showed similarities between the ulcers from localised CL (LCL) and DL. The papules had fewer CD4+ T cells than the DL ulcers. Although both CD4+ cells and macrophages contribute to inflammation in early CL, macrophages are the primary cell type associated with inflammation intensity in late ulcers. The higher frequency of CD20+ cells and plasma cells in lesions demonstrates the importance of B cells in the pathogenesis of leishmaniasis. The number of neutrophils was the same in all of the analysed groups. A comparison between the ulcers from LCL and DL and the early ulcers and papules shows that few differences between these two clinical forms can be distinguished by observing only the tissue.

Comparative analysis of the tissue inflammatory response in human cutaneous and disseminated leishmaniasis.

Cutaneous leishmaniasis (CL) is the most frequent clinical form of tegumentary leishmaniasis and is characterised by a single or a few ulcerated skin lesions that may disseminate into multiple ulcers and papules, which characterise disseminated leishmaniasis (DL). In this study, cells were quantified using immunohistochemistry and haematoxylin and eosin staining (CD4+, CD68+, CD20+, plasma cells and neutrophils) and histopathology was used to determine the level of inflammation in biopsies from patients with early CL, late CL and DL (ulcers and papules). The histopathology showed differences in the epidermis between the papules and ulcers from DL. An analysis of the cells present in the tissues showed similarities between the ulcers from localised CL (LCL) and DL. The papules had fewer CD4+ T cells than the DL ulcers. Although both CD4+ cells and macrophages contribute to inflammation in early CL, macrophages are the primary cell type associated with inflammation intensity in late ulcers. The higher frequency of CD20+ cells and plasma cells in lesions demonstrates the importance of B cells in the pathogenesis of leishmaniasis. The number of neutrophils was the same in all of the analysed groups. A comparison between the ulcers from LCL and DL and the early ulcers and papules shows that few differences between these two clinical forms can be distinguished by observing only the tissue.

Exposure of phosphatidylserine on Leishmania amazonensis isolates is associated with diffuse cutaneous leishmaniasis and parasite infectivity.

Diffuse cutaneous leishmaniasis (DCL) is a rare clinical manifestation of leishmaniasis, characterized by an inefficient parasite-specific cellular response and heavily parasitized macrophages. In Brazil, Leishmania (Leishmania) amazonensis is the main species involved in DCL cases. In the experimental model, recognition of phosphatidylserine (PS) molecules exposed on the surface of amastigotes forms of L. amazonensis inhibits the inflammatory response of infected macrophages as a strategy to evade the host immune surveillance. In this study, we examined whether PS exposure on L. amazonensis isolates from DCL patients operated as a parasite pathogenic factor and as a putative suppression mechanism of immune response during the infection. Peritoneal macrophages from F1 mice (BALB/c×C57BL/6) were infected with different L. amazonensis isolates from patients with localized cutaneous leishmaniasis (LCL) or DCL. DCL isolates showed higher PS exposure than their counterparts from LCL patients. In addition, PS exposure was positively correlated with clinical parameters of the human infection (number of lesions and time of disease) and with characteristics of the experimental infection (macrophage infection and anti-inflammatory cytokine induction). Furthermore, parasites isolated from DCL patients displayed an increased area in parasitophorous vacuoles (PV) when compared to those isolated from LCL patients. Thus, this study shows for the first time that a parasite factor (exposed PS) might be associated with parasite survival/persistence in macrophages and lesion exacerbation during the course of DCL, providing new insights regarding pathogenic mechanism in this rare chronic disease.

Glicoconjugados (GIPLs e LPGs) de Leishmania braziliensis: Modulação do Sistema Imune Inato e variaçõesna estrutura de carboidratos / Glycoconjugates (GIPLs and LPGS) of Leishmania braziliensis: Innate Immune System Modulation and variations the carbohydrate structure

Os glicoconjugados de Leishmania tem sido extensivamente estudados, mas ainda poucose sabe sobre o quanto polimorfismos intra e interespecíficos contribuem com o desenvolvimentodas diferentes imunopatologias das leishmanioses. Por este motivo, duas espécies de importânciaepidemiológica foram examinadas, L. braziliensis e L. infantum, agentes causadores dasleishmanioses cutânea e visceral, respectivamente. O LPG de L. braziliensis não possui cadeiaslaterais enquanto o LPG de L. infantum carrega em sua estrutura oligômeros de até três β-glicoses como cadeias laterais. Por outro lado a estrutura dos GIPLs destas espécies eradesconhecida e foi objeto de estudo deste trabalho.A análise estrutural dos GIPLs mostrou que L. infantum possui GIPLs pequenos e ricosem manose, sugerindo predominância de GIPLs do tipo I e híbridos enquanto L. braziliensisapresenta GIPLs grandes e ricos em galactose, sugestivo do tipo II. Para analisar o papel destasmoléculas na interação com o hospedeiro, macrófagos peritoneais murinos foram tratados comLPG ou GIPLs e a produção de nitrito, citocinas, bem como a ativação de MAPKs foramavaliados.De forma geral, macrófagos estimulados com LPG de L. braziliensis, demonstraram umaprodução maior de TNF-α, IL-1β, IL-6 e NO do que os estimulados com LPG de L. infantum,adicionalmente, células tratadas com LPG de ambas as espécies mostraram uma resposta proinflamatória mais proeminente. Além disto, os GIPLs mostraram a capacidade de inibir aprodução de IL-12 e NO em macrófagos estimulados com IFN-γ e LPS. Finalmente, osglicoconjugados destas duas espécies resultaram em uma cinética diferencial na ativação deMAPKs. O LPG de L. braziliensis mostrou uma ativação transiente enquanto o de L. infantumuma ativação gradual. Os GIPLs de ambas espécies falharam em ativar MAPKs

Glicoconjugados (GIPLs e LPGs) de Leishmania braziliensis: Modulação do Sistema Imune Inato e variaçõesna estrutura de carboidratos

Os glicoconjugados de Leishmania tem sido extensivamente estudados, mas ainda poucose sabe sobre o quanto polimorfismos intra e interespecíficos contribuem com o desenvolvimentodas diferentes imunopatologias das leishmanioses. Por este motivo, duas espécies de importânciaepidemiológica foram examinadas, L. braziliensis e L. infantum, agentes causadores dasleishmanioses cutânea e visceral, respectivamente. O LPG de L. braziliensis não possui cadeiaslaterais enquanto o LPG de L. infantum carrega em sua estrutura oligômeros de até três β-glicoses como cadeias laterais. Por outro lado a estrutura dos GIPLs destas espécies eradesconhecida e foi objeto de estudo deste trabalho.A análise estrutural dos GIPLs mostrou que L. infantum possui GIPLs pequenos e ricosem manose, sugerindo predominância de GIPLs do tipo I e híbridos enquanto L. braziliensisapresenta GIPLs grandes e ricos em galactose, sugestivo do tipo II. Para analisar o papel destasmoléculas na interação com o hospedeiro, macrófagos peritoneais murinos foram tratados comLPG ou GIPLs e a produção de nitrito, citocinas, bem como a ativação de MAPKs foramavaliados.De forma geral, macrófagos estimulados com LPG de L. braziliensis, demonstraram umaprodução maior de TNF-α, IL-1β, IL-6 e NO do que os estimulados com LPG de L. infantum,adicionalmente, células tratadas com LPG de ambas as espécies mostraram uma resposta proinflamatória mais proeminente. Além disto, os GIPLs mostraram a capacidade de inibir aprodução de IL-12 e NO em macrófagos estimulados com IFN-γ e LPS. Finalmente, osglicoconjugados destas duas espécies resultaram em uma cinética diferencial na ativação deMAPKs. O LPG de L. braziliensis mostrou uma ativação transiente enquanto o de L. infantumuma ativação gradual. Os GIPLs de ambas espécies falharam em ativar MAPKs

Human cutaneous leishmaniasis: interferon-dependent expression of double-stranded RNA-dependent protein kinase (PKR) via TLR2.

We investigated the type I interferon (IFN-1)/PKR axis in the outcome of the Leishmania (Leishmania) amazonensis infection, along with the underlying mechanisms that trigger and sustain this signaling pathway. Reporter assays of cell extracts from RAW-264.7 macrophages infected with L. (L.) amazonensis or HEK-293T cells cotransfected with TLR2 and PKR promoter constructions were employed. Primary macrophages of TLR2-knockout (KO) or IFNR-KO mice were infected, and the levels of PKR, IFN-1, and superoxide dismutase 1 (SOD1) transcript levels were investigated and compared. Immunohistochemical analysis of human biopsy lesions was evaluated for IFN-1 and PKR-positive cells. Leishmania infection increased the expression of PKR and IFN-ß on induction of PKR-promoter activity. The observed effects required the engagement of TLR2. TLR2-KO macrophages expressed low IFN-ß and PKR levels postinfection with a reduced parasite load. We also revealed the requirement of PKR signaling for Leishmania-induced IFN-1 expression, responsible for sustaining PKR expression and enhancing infection. Moreover, during infection, SOD1 transcripts increased and were also enhanced when IFN-1 was added to the cultures. Remarkably, SOD1 expression was abrogated in infected, dominant-negative PKR-expressing cells. Finally, lesions of patients with anergic diffuse cutaneous leishmaniasis exhibited higher levels of PKR/IFN-1-expressing cells compared to those with single cutaneous leishmaniasis. In summary, we demonstrated the mechanisms and relevance of the IFN-1/PKR axis in the Leishmania infection.

CD8 cells of patients with diffuse cutaneous leishmaniasis display functional exhaustion: the latter is reversed, in vitro, by TLR2 agonists.

Leishmania mexicana (Lm) causes localized (LCL) and diffuse (DCL) cutaneous leishmaniasis. DCL patients have a poor cellular immune response leading to chronicity. It has been proposed that CD8 T lymphocytes (CD8) play a crucial role in infection clearance, although the role of CD8 cytotoxicity in disease control has not been elucidated. Lesions of DCL patients have been shown to harbor low numbers of CD8, as compared to patients with LCL, and leishmanicidal treatment restores CD8 numbers. The marked response of CD8 towards Leishmania parasites led us to analyze possible functional differences between CD8 from patients with LCL and DCL. We compared IFNγ production, antigen-specific proliferation, and cytotoxicity of CD8 purified from PBMC against autologous macrophages (MO) infected with Leishmania mexicana (MOi). Additionally, we analyzed tissue biopsies from both groups of patients for evidence of cytotoxicity associated with apoptotic cells in the lesions. We found that CD8 cell of DCL patients exhibited low cytotoxicity, low antigen-specific proliferation and low IFNγ production when stimulated with MOi, as compared to LCL patients. Additionally, DCL patients had significantly less TUNEL+ cells in their lesions. These characteristics are similar to cellular "exhaustion" described in chronic infections. We intended to restore the functional capacity of CD8 cells of DCL patients by preincubating them with TLR2 agonists: Lm lipophosphoglycan (LPG) or Pam3Cys. Cytotoxicity against MOi, antigen-specific proliferation and IFNγ production were restored with both stimuli, whereas PD-1 (a molecule associated with cellular exhaustion) expression, was reduced. Our work suggests that CD8 response is associated with control of Lm infection in LCL patients and that chronic infection in DCL patients leads to a state of CD8 functional exhaustion, which could facilitate disease spread. This is the first report that shows the presence of functionally exhausted CD8 T lymphocytes in DCL patients and, additionally, that pre-stimulation with TLR2 ligands can restore the effector mechanisms of CD8 T lymphocytes from DCL patients against Leishmania mexicana-infected macrophages.

Chemokines and chemokine receptors coordinate the inflammatory immune response in human cutaneous leishmaniasis.

Cutaneous leishmaniasis (CL) includes different clinical manifestations displaying diverse intensities of dermal inflammatory infiltrate. Diffuse CL (DCL) cases are hyporesponsive, and lesions show very few lymphocytes and a predominance of macrophages. In contrast, localized CL (LCL) cases are responsive to leishmanial antigen, and lesions exhibit granulocytes and mononuclear cell infiltration in the early phases, changing to a pattern with numerous lymphocytes and macrophages later in the lesion. Therefore, different chemokines may affect the predominance of cell infiltration in distinct clinical manifestations. In lesions from LCL patients, we examined by flow cytometry the presence of different chemokines and their receptors in T cells, and we verified a higher expression of CXCR3 in the early stages of LCL (less than 30 days of infection) and a higher expression of CCR4 in the late stages of disease (more than 60 days of infection). We also observed a higher frequency of T cells producing IL-10 in the late stage of LCL. Using immunohistochemistry, we observed a higher expression of CCL7, CCL17 in lesions from late LCL, as well as CCR4 suggesting a preferential recruitment of regulatory T cells in the late LCL. Comparing lesions from LCL and DCL patients, we observed a higher frequency of CCL7 in DCL lesions. These results point out the importance of the chemokines, defining the different types of cells recruited to the site of the infection, which could be related to the outcome of infection as well as the clinical form observed.

Leishmania mexicana lipophosphoglycan differentially regulates PKCalpha-induced oxidative burst in macrophages of BALB/c and C57BL/6 mice.

Leishmania are protozoan parasites that infect macrophages and their survival is partially achieved through inhibition of the cellular oxidative burst by parasite lipophosphoglycan (LPG). PKCalpha is the predominant PKC isoenzyme required for macrophage oxidative burst, yet it is not known if different susceptibility of BALB/c and C57BL/6 mice to Leishmania mexicana could be related to PKCalpha. We analysed the effect of L. mexicana promastigotes and parasite LPG on expression of PKCalpha and on its activity in macrophages of both mouse strains. Our data show that expression of the isoenzyme was not altered either by LPG or by L. mexicana promastigotes. Yet LPG exerted opposing effects on PKCalpha activity of macrophages between both strains: in susceptible BALB/c cells, it inhibited PKCalpha activity, whereas in the more resistant strain it augmented enzymatic activity 2.8 times. In addition, LPG inhibited oxidative burst only in susceptible BALB/c macrophages and the degree of inhibition correlated with parasite survival. Promastigotes also inhibited PKCalpha activity and oxidative burst in macrophages of BALB/c mice, whereas in C57BL/6, they enhanced PKCalpha activity and oxidative burst inhibition was less severe. Our data indicate that control of PKCalpha-induced oxidative burst by L. mexicana LPG relates with its success to infect murine macrophages.